Camera module

ABSTRACT

A camera module may comprise: a printed circuit board on which an image sensor is mounted; a holder member disposed above the printed circuit board and having a plurality of magnets installed thereon; a bobbin installed on the inside of the holder member to be capable of moving along an optical axis, and having a coil unit installed on the outer peripheral surface thereof to be capable of electrically interacting with the magnets; a plurality of receptacles formed in the peripheral surface of the bobbin to form spaces that are separated from the coil unit; and a cover member having a plurality of integrally formed inner yokes, which are formed at positions corresponding to the plurality of receptacles and have the surface on one side thereof separated a certain distance from the coil unit and the surface on the other side thereof separated a certain distance from the bobbin.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No. 16/210,770, filed Dec. 5, 2018; which is a continuation of U.S. application Ser. No. 14/904,602, filed Jan. 12, 2016, now U.S. Pat. No. 10,180,561, issued Jan. 15, 2019; which is the U.S. national stage application of International Patent Application No. PCT/KR2014/006238, filed Jul. 11, 2014; which claims priority to Korean Application No. 10-2013-0081956, filed Jul. 12, 2013; the disclosures of each of which are incorporated herein by reference in their entirety.

BACKGROUND Field of the Disclosure

The present disclosure relates to a camera module.

Discussion of the Related Art

A camera module may include an image sensor, an infrared cut-off filter configured to block light in infrared area from being incident on the image sensor, and an optical system formed of at least one lens configured to deliver an image to the image sensor.

Here, the optical system may be installed with an actuator module configured to perform auto focusing function and handshake compensation function.

The actuator module may be composed in various ways. In general, a voice coil motor is commonly used. The voice coil motor is driven by electromagnetic interaction between magnets fixed at a holder member and a coil unit wound on an outer circumferential surface of a bobbin, and may perform auto focusing function.

Generally, a yoke made of a major material of iron (Fe) that is a ferromagnetic body is provided in order to form a magnetic path of the magnet. Recently, a voice coil motor, without any separate yoke installed thereat, having an inner yoke integrally formed with a cover member such as a shield can made of iron (Fe) that is a ferromagnetic body at a position at which the yoke is to be installed, is also being developed.

Such voice coil motor having an inner yoke is advantageous in that the assembly of the camera module becomes convenient and the number of components can be reduced. However, when the length of the inner yoke is too short, the electromagnetic efficiency declines, an interference with an upper portion of the coil unit wound on an outer circumferential surface of the bobbin may occur during being driven, and foreign materials may be introduced.

In addition, when the length of the inner yoke is too long, the electromagnetic efficiency declines, as well as the verticality and concentricity becomes difficult to manage, thereby the manufacturability is degraded.

SUMMARY OF THE DISCLOSURE

According to an exemplary embodiment of the present disclosure, a camera module having an advanced structure so as to inhibit introduction of foreign materials is provided, in consideration of the electromagnetic attribute.

In a general aspect of the present disclosure, there is provided a camera module, the camera module comprising: a PCB (Printed Circuit Board); a holder member arranged at an upper side of the PCB and installed with a plurality of magnets; a bobbin movably installed at an inner side of the holder member and installed with a coil unit facing the magnet at an outer circumferential surface of the bobbin; a plurality of accommodation grooves formed at a circumferential surface of the bobbin and being spaced from the coil unit at a predetermined interval to form a spaced portion; and a cover member integrally formed with a plurality of inner yokes formed by being bent at a position corresponding to that of the plurality of accommodation grooves, wherein one side surface of the inner yoke is spaced from the coil unit at a predetermined interval and another side surface of the inner yoke is spaced from the bobbin at a predetermined interval.

In some exemplary embodiments of the present disclosure, each of the inner yoke and the accommodation groove is formed at four edge portions of the cover member and the holder member, respectively.

In some exemplary embodiments of the present disclosure, the inner yoke may include: a connection portion connected to an upper portion of the cover member and formed by being bent in a round shape; and a pair of escape grooves symmetrically formed at a position adjacent to that of the connection portion.

In some exemplary embodiments of the present disclosure, the escape groove may have a length (L1) of 20-50% of an entire length (L2).

In some exemplary embodiments of the present disclosure, the escape groove may include a slanted surface having a predetermined angle.

In some exemplary embodiments of the present disclosure, an entire length (L2) of the inner yoke may be formed to be longer than a length (H1) from an upper surface of the cover member to an upper surface of the coil unit.

In some exemplary embodiments of the present disclosure, an entire length (L2) of the inner yoke may be 20-40% of an entire length (H) of the magnet.

In some exemplary embodiments of the present disclosure, a length (H2) of an end of the inner yoke overlapped with the coil unit by being inserted in the accommodation groove may be formed to be longer than a backstroke distance of the bobbin.

In some exemplary embodiments of the present disclosure, a surface of the inner yoke facing the bobbin may have a curvature corresponding to that of a virtual circle (a) concentric with the bobbin.

In some exemplary embodiments of the present disclosure, a surface of the inner yoke facing the bobbin may be provided in a flat and straight shape, and the inner yokes facing each other may be mutually parallel.

In some exemplary embodiments of the present disclosure, an angle (a) formed by the surface of the inner yoke facing the bobbin and a lateral surface of the cover member may be 45 degrees.

In some exemplary embodiments of the present disclosure, the holder member may include a plurality of magnet installation holes at four surfaces thereof for magnets of a same size to be inserted.

In some exemplary embodiments of the present disclosure, the cover member may be formed of a ferromagnetic body.

In some exemplary embodiments of the present disclosure, the bobbin may include a lens barrel installed inside with at least one lens.

In some exemplary embodiments of the present disclosure, the camera module may comprise: upper and lower elastic members respectively fixed at upper and lower portions of the holder member to elastically support upward and downward motions of the bobbin.

In some exemplary embodiments of the present disclosure, the coil unit may be a ring-shaped coil block coupled by being inserted in an outer circumferential surface of the bobbin.

In some exemplary embodiments of the present disclosure, the coil unit may include: a straight surface arranged at a position corresponding to that of the magnet; and a curved surface arranged at a position corresponding to that of the inner yoke and the accommodation groove.

In some exemplary embodiments of the present disclosure, the bobbin may include: a first surface flatly formed at a surface corresponding to the straight surface; and a second surface roundly formed at a surface corresponding the curved surface.

In some exemplary embodiments of the present disclosure, the first surface may include: a protruded portion inhibiting the coil unit from departing in an optical axis direction.

In some exemplary embodiments of the present disclosure, the camera module may comprise: a base interposed between the PCB and the holder member and installed with an infrared cut-off filter.

According to an exemplary embodiment of the present disclosure, an interference between the inner yoke and the bobbin occurring when the auto focusing operation is being performed or a shaking of the bobbin occurs due to an external impact may be minimized, because an escape groove is formed at the inner yoke.

In addition, according to an exemplary embodiment of the present disclosure, foreign materials generated by motions of the bobbin or flowing down along the inner yoke may be collected by the grooved portion, because an end of the inner yoke is inserted in a grooved portion formed in an internal spaced portion of the coil unit wound on an outer circumferential surface of the bobbin.

In addition, according to an exemplary embodiment of the present disclosure, the voice coil motor may have optimal electromagnetic characteristic, because an entire length of the inner yoke is formed to be more than 20% of an entire length of the magnet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating an example of a camera module according to an exemplary embodiment of the present disclosure.

FIG. 2 is an exploded perspective view of FIG. 1 .

FIG. 3 is an enlarged view illustrating portion A of FIG. 2 .

FIG. 4 is a B-B sectional view of FIG. 1 .

FIG. 5 is an enlarged view illustrating portion C of FIG. 4 .

FIG. 6 is a plan view illustrating a cover member having an inner yoke according to a first exemplary embodiment of the present disclosure.

FIG. 7 is a plan view illustrating a cover member having an inner yoke according to a second exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, an exemplary embodiment of the present disclosure will be described with reference to the drawings.

FIG. 1 is a perspective view illustrating an example of a camera module according to an exemplary embodiment of the present disclosure; FIG. 2 is an exploded perspective view of FIG. 1 ; FIG. 3 is an enlarged view illustrating portion A of FIG. 2 ; FIG. 4 is a B-B sectional view of FIG. 1 ; FIG. 5 is an enlarged view illustrating portion C of FIG. 4 ; FIG. 6 is a plan view illustrating a cover member having an inner yoke according to a first exemplary embodiment of the present disclosure; and FIG. 7 is a plan view illustrating a cover member having an inner yoke according to a second exemplary embodiment of the present disclosure.

As illustrated in FIGS. 1 and 2 , a camera module according to an exemplary embodiment of the present disclosure may include a PCB (Printed Circuit Board) (10), a base (20), a holder member (30), a bobbin (40) and a cover member (50).

An image sensor (11) may be mounted at the PCB (10). The PCB (10) may form a bottom surface of the camera module. The image sensor (11) may be mounted at a center of an upper surface of the PCB (10), so as to be disposed with at least one lens (not illustrated) accommodated in the lens barrel (42) along an optical axis direction. The image sensor may convert an optical signal of an object that has been incident through the lens to an electrical signal.

The base (20) may include an infrared cut-off filter (25) installed at a position corresponding to that of the image sensor (11). In such case, the infrared cut-off filter (25) may be installed at a through-hole formed at a center of the based (20). Alternatively, a blue filter may be provided instead of the infrared cut-off filter. Here, the infrared cut-off filter (25) may be formed of, for example, a film material or a glass material. In addition, an infrared cut-off coating material may be arranged on a flat optical filter such as a cover glass for image plane protection, cover glass, etc.

A lower portion of the base (20) may be connected to the PCB (10), and an upper portion of the base (20) may support a bottom surface of the holder member (30) (to be described hereinafter). The base (20) may include a separate terminal member in order for electrical connection with the PCB (10). The terminal member may be provided as a separate member. Alternatively, the terminal member may be provided as a surface electrode formed on a surface of the base (20).

In addition, the base (20) may include at a lateral surface thereof an accommodation groove (21) to accommodate a terminal portion (not illustrated) electrically connected to the lower elastic member (45) or the coil unit (42). The terminal portion may be formed by being introduced at a lateral surface of the lower elastic member (45). In addition, the accommodation groove (21) may gradually form a right angle or an acute angel along a downward direction, so as to correspond to a bent angle of the terminal portion.

In addition, the base (20) may include at least one fixing protrusion (22) formed by being protruded at an upper edge of the base (20) to have a surface-to-surface contact with or be coupled to an internal lateral surface of the cover member (50). The fixing protrusion (22) may guide the cover member (50) to be readily coupled as well as may facilitate concrete fixation after the coupling.

In addition, a recessed portion (23) may be formed by being recessed at a center of the base (20) so that the bobbin (210) can be disposed by being spaced.

In addition, the base (20) is not an essential structure for the present disclosure. Therefore, although not illustrated in the drawings, the holder member (30) may be configured to perform a function of the base (20).

The holder member (30) may be formed in a broadly quadrangular shape, and may include a plurality of magnet installation holes (32) at each of four surfaces of the holder member (30), so that a plurality of magnets (33) can be installed at the magnet installation holes (32). As illustrated in the drawings, the magnet installation hole (32) may be formed at a lateral surface of the holder member (30). Alternatively, the magnet installation hole (32) may be formed at each edge of the holder member (30). In addition, the holder member (30) may be formed of an insulated material, and may be implemented as an injection molding material, in consideration of productivity.

In addition, at least two stoppers (37) that are protruded so as to absorb impact energy of external impacts may be formed at an upper lateral surface of the holder member (30) by being spaced at a predetermined interval. The stopper (37) may be integrally formed with the holder member (30), or may be formed at the bobbin (40). Alternatively, the stopper (37) may not be formed at all.

In addition, the holder member (30) may be formed in a shape corresponding to that of an inner lateral surface of the cover member (50). Otherwise, the holder member (30) may form an external appearance of the lens actuating unit by being integrally formed with the cover member (50), without being separately provided.

Each of the magnets (33) may be formed in a size corresponding to each other. In addition, the magnets (33) facing each other may be arranged in mutual parallel position.

As illustrated in FIG. 2 , the holder member (30) may be provided in a hexahedron shape, with its four surfaces formed in shapes of thin frames. In addition, upper and lower elastic members (44)(45) may be respectively installed at upper and lower portions of the holder member (30) to elastically support upward and downward motions of the bobbin (40) in an optical axis direction.

According to an exemplary embodiment of the present disclosure, a bottom surface of the holder member (30) may be coupled to the base (20), and an upper surface of the holder member (30) may be coupled to the cover member (50) (to be described hereinafter) at a fixed position. Here, the upper elastic member (44) may be interposed between the holder member (30) and the cover member (50), and the lower elastic member (45) may be interposed between the holder member (30) and the base (20).

The bobbin (40) may be installed in the internal space of the holder member (30) so as to be movable reciprocatingly in a direction parallel to the optical axis. The bobbin (40) may be installed with a coil unit (43) at an outer circumferential surface of the bobbin (40) so as to enable electromagnetic interaction with the magnet (33).

The bobbin (40) may include a lens barrel (42) installed inside with at least one lens (42 a). As illustrated in FIG. 2 , the lens barrel (42) may be formed to be capable of being screw-coupled to an internal side of the bobbin (40). However, the present disclosure is not limited hereto. Although not illustrated in the drawings, the lens barrel (42) may be directly coupled to the internal side of the bobbin (40) by means such as gluing except the screw coupling. Otherwise, the at least one lens (42 a) may be integrally formed with the bobbin (40) without the lens barrel (42). The lens (42 a) may be formed of a single lens, or may be composed of a plurality of lenses to form an optical system.

The bobbin (40) may be installed, at upper and lower portions thereof, with the upper and lower elastic members (44) (45), respectively. Each of the upper and lower elastic members (44) (45) may have one end thereof connected to the holder member (30) and another end thereof connected to the bobbin (40), respectively.

For example, as illustrated in FIG. 2 , first and second protrusions (34 a) (35 a) for coupling the elastic members may be respectively formed at upper and lower portions of the holder member (30), and first and second protrusion accommodation hole (44 a) (45 a) may be respectively formed at positions corresponding to those of the first and second elastic members (44) (45), so that the upper and lower elastic members (44) (45) may be coupled to the holder member (30) via coupling of those protrusions and protrusion accommodation holes. In the same manner, the upper and lower elastic members (44) (45) may be coupled to the upper and lower portions of the bobbin (40) via such structure as described in the above.

According to such structure as described in the above, the upper and lower elastic member (44) (45) may elastically support the bobbin (40) while performing cantilever action with a fixed position of the holder member (30) as an axis, when the bobbin (40) performs reciprocating motions with respect to the optical axis direction.

Meanwhile, the coil unit (43) may be directly wound on an outer circumferential surface of the bobbin (40). Alternatively, the coil unit (43) may be provided as a ring-shaped coil block coupled by being inserted in an outer circumferential surface of the bobbin (40), as illustrated in FIG. 2 . The coil unit (43) formed as a coil block may include a straight surface (43 a) arranged at a position corresponding to that of the magnet (33) and a curved surface (43 b) arranged at a position corresponding to that of the inner yoke (100) and the accommodation groove (200).

In addition, the bobbin (40) may include a first surface (40 a) flatly formed at a surface corresponding to the straight surface (43 a) and a second surface (40 b) roundly formed at a surface corresponding the curved surface (43 b), so that the coil unit (43) can be coupled to an outer circumferential surface of the bobbin (40). Here, the first surface (40 a) may include a protruded portion (47) inhibiting the coil unit (43) from departing in an optical axis direction, so as to inhibit the coil unit (43) from being departed from the installation position due to external impacts such as an impact that occur during the reciprocating motions of the bobbin (40).

In addition, the bobbin (40) may include a plurality of accommodation grooves (200) formed at a circumferential surface of the bobbin (40) and being spaced from the coil unit (43) at a predetermined interval to form a spaced portion. The inner yoke (100) formed at the cover member (50) may be inserted in the accommodation groove (200). The relationship between the inner yoke (100) and the accommodation groove (200) will be hereinafter described again.

The cover member (50) may be formed of a ferromagnetic body such as an iron, may be provided in a shape corresponding to that of the holder member (30), so as to cover the holder member (30). That is, as illustrated in FIGS. 1 to 4 , when the holder member (30) is in a tetragonal shape, the cover member (50) may be also provided in a tetragonal shape.

The cover member (50) may be integrally formed with a plurality of inner yokes (100) formed at a position corresponding to that of the plurality of accommodation grooves (200). According to an exemplary embodiment of the present disclosure, one side surface of the inner yoke (100) may be spaced from the coil unit (43) at a predetermined interval, and another side surface of the inner yoke (100) may be spaced from the bobbin (40) at a predetermined interval. In addition, each of the inner yoke (100) and the accommodation groove (200) may be formed at four edge portions of the cover member (50) and the holder member (30), respectively.

As illustrated in FIGS. 2 and 3 , the inner yoke (100) may be formed by being bent from an upper surface of the cover member (50) to an internal side in a direction parallel to the optical axis. A connection portion between the cover member (50) and the inner yoke (100) may be formed in a round shape, a slanted shape or a rectangularly bent shape.

The inner yoke (100) may include a pair of escape grooves (110) symmetrically formed at a position adjacent to that of the connection portion. The portion where the escape groove (110) is formed may form a bottleneck section. The bottleneck section where the escape groove (110) is formed may minimize interference between the inner yoke (100) and the bobbin (40) occurring when the bobbin (40) is being driven.

As illustrated in FIG. 3 , a length (L1) of the escape groove (110) may be of 20-50% of an entire length (L2) of the inner yoke (100). The escape groove (110) may include a slanted surface (111) having a predetermined angle.

Due to forming of the slanted surface (111), the inner yoke (100) may have a width gradually being widened as approaching an end portion of the inner yoke (100). Here, a width of the end portion of the inner yoke (100) may be formed to be corresponding to a width of the accommodation groove (200), or may formed to be narrower than the width of the accommodation groove (200).

As illustrated in FIG. 3 , the escape groove (110) may have a cutting width (w) in 0.1-0.5 mm with respect to a width direction of the inner yoke (100). However, the above numerical values are intended to be illustrative, and the present disclosure is not limited hereto. Therefore, the cutting width of the escape groove (110) may be modified according to variation in size of the camera module.

Referring to FIGS. 3 to 5 , an entire length (L2) of the inner yoke (100) may be formed to be longer than a length (H1) from an upper surface of the cover member (30) to an upper surface of the coil unit (43). According to such structure, the inner yoke (100) may be inserted into an internal space of the accommodation groove (200), and may be arranged to be overlapped with the coil unit (43) at a predetermined length inside of the spaced portion formed between the coil unit (43) and the bobbin (40).

In addition, an entire length (L2) of the inner yoke may be provided to be 20-40% of an entire length (H) of the magnet (33). This is because, if the entire length (L2) of the inner yoke (100) is too short beyond the above-mentioned range, the electromagnetic efficiency declines, an interference with an upper portion of the coil unit (43) may occur during being driven, and foreign materials may be introduced in the gap therebetween. In addition, if the length (L2) of the inner yoke (100) is too long, the electromagnetic efficiency also declines, as well as the verticality and concentricity becomes difficult to manage, thereby the manufacturability is degraded.

In addition, a length (H2) of an end of the inner yoke (100) overlapped with the coil unit (43) by being inserted in the accommodation groove (200) may be formed to be longer than a backstroke distance of the bobbin (40). In such case, an upper end portion of the coil unit (43) may be arranged upper than the end of the inner yoke (100) at the lowest position during the reciprocating motions of the bobbin (40).

In addition, the end of the inner yoke (100) may be arranged, at the reference position, by being spaced from a bottom surface of the accommodation groove (200) at a predetermined interval. This is to avoid contact and interference between the end of the inner yoke (100) and the bottom surface of the accommodation groove (200) at the highest position during the reciprocating motions of the bobbin (40).

According to a first exemplary embodiment, as illustrated in FIG. 6 , a surface of the inner yoke (100) facing the bobbin (40) may have a curvature corresponding to that of a virtual circle (a) concentric with the bobbin (40).

According to a second exemplary embodiment, a surface of the inner yoke (100) facing the bobbin (40) may be provided in a flat and straight shape, and the inner yokes (100) facing each other may be mutually parallel. Here, an angle (a) formed by the surface of the inner yoke (100) facing the bobbin (40) and a lateral surface of the cover member (50) may be 45 degrees.

As described in the above, the inner yoke (100) integrally formed with the cover member (50) may be arranged at an internal side of the spaced portion formed by the accommodation groove (200) formed at an outer circumferential surface of the bobbin (40). Thereby, as illustrated in FIGS. 4 and 5 , a structure to primarily collect foreign materials flowing down along the inner yoke (100) may be provided, so as to minimize introduction of foreign materials in the camera module.

In addition, an entire length (L2) of the inner yoke (100) may be formed to be 20-50% of an entire length (H) of the magnet (33), while the entire length (L2) of the inner yoke (100) may be formed to be longer than a length (H1) from an upper surface of the cover member (30) to an upper surface of the coil unit (43). Thereby, the electromagnetic efficiency of the camera module may be maximized, as well as the interference between each of components during upward and downward motions of the bobbin (40) may be minimized.

In addition, motions of both wing portions of the inner yoke (100) may be restricted in the spaced portion formed by an inner circumferential surface of the accommodation groove (200) and a surface of the coil unit (43) facing the bobbin (40). Thereby, the bobbin (40) may be inhibited from rotating with respect to the optical axis direction due to an external impact or a malfunction, etc.

The abovementioned exemplary embodiments are intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, variations, and equivalents will be apparent to those skilled in the art. The features, structures, methods, and other characteristics of the exemplary embodiments described herein may be combined in various ways to obtain additional and/or alternative exemplary embodiments within an equivalent scope. Therefore, the technical scope of the rights for the present disclosure shall be decided by the appended claims and equivalents thereof. 

What is claimed is:
 1. A voice coil motor comprising: a cover member comprising an upper plate and a lateral plate extending from the upper plate; a bobbin disposed in the cover member; a coil disposed on an outer peripheral surface of the bobbin; a magnet facing the coil and disposed between the coil and the lateral plate of the cover member; and an elastic member coupled to the bobbin, wherein the cover member comprises an inner yoke extending from the upper plate of the cover member and disposed in the lateral plate of the cover member, wherein the bobbin comprises an accommodation groove formed on the outer peripheral surface of the bobbin, wherein the inner yoke is disposed in the accommodation groove, wherein the cover member comprises an escape groove formed on the inner yoke, wherein at least a portion of the escape groove is disposed higher than an upper end of the magnet, and wherein a width of a portion of the inner yoke at a position having the escape groove is smaller than a width of an end portion of the inner yoke.
 2. The voice coil motor of claim 1, wherein at least a portion of the inner yoke is disposed between one portion of the bobbin and another portion of the bobbin in a circumferential direction.
 3. The voice coil motor of claim 1, wherein the inner yoke is configured to be contacted with the bobbin so that the bobbin is inhibited from rotating with respect to an optical axis direction.
 4. The voice coil motor of claim 1, wherein at least a portion of the inner yoke is disposed between the bobbin and the coil.
 5. The voice coil motor of claim 1, wherein the inner yoke comprises a connection portion bent from the upper plate of the cover member, and wherein the escape groove is disposed at a position adjacent to that of the connection portion of the inner yoke.
 6. The voice coil motor of claim 1, wherein the escape groove comprises a pair of escape grooves symmetrically formed on both lateral surfaces of the inner yoke.
 7. The voice coil motor of claim 1, wherein the escape groove comprises a first escape groove and a second escape groove, wherein the width of the portion of the inner yoke between the first escape groove and the second escape groove is smaller than the width of the end portion of the inner yoke.
 8. The voice coil motor of claim 1, wherein at least a portion of the escape groove is not overlapped with the magnet in a direction perpendicular to an optical axis direction.
 9. The voice coil motor of claim 1, wherein the escape groove has a length (L1) of 20-50% of an entire length (L2) of the inner yoke in an optical axis direction.
 10. The voice coil motor of claim 1, wherein the elastic member comprises an upper elastic member coupled to an upper portion of the bobbin and a lower elastic member coupled to a lower portion of the bobbin, and wherein the escape groove is closer to the upper elastic member than to the lower elastic member.
 11. The voice coil motor of claim 10, wherein the escape groove is overlapped with the upper elastic member in a direction perpendicular to an optical axis direction.
 12. The voice coil motor of claim 1, wherein an entire length (L2) of the inner yoke is 20-40% of an entire length (H) of the magnet in an optical axis direction.
 13. The voice coil motor of claim 1, wherein a length (H2) of the inner yoke overlapped with the coil by being inserted in the accommodation groove is greater than a backstroke distance of the bobbin.
 14. The voice coil motor of claim 1, wherein a portion of the inner yoke has a width gradually being widened as approaching the end portion of the inner yoke.
 15. The voice coil motor of claim 1, wherein the bobbin comprises first and second protrusions protruding from the outer peripheral surface of the bobbin, wherein the second protrusion is disposed below the first protrusion, wherein the coil is disposed between the first protrusion and the second protrusion, and wherein a lower end of the inner yoke is disposed at a position lower than that of a lower end of the first protrusion and at a position higher than that of an upper end of the second protrusion.
 16. A camera module comprising: a PCB (Printed Circuit Board); an image sensor disposed on the PCB; the voice coil motor of claim 1 disposed above the PCB; and a lens coupled to the bobbin of the voice coil motor.
 17. A voice coil motor comprising: a cover member comprising an upper plate and a lateral plate extending from the upper plate; a bobbin disposed in the cover member; a coil disposed on an outer peripheral surface of the bobbin; a magnet facing the coil and disposed between the coil and the lateral plate of the cover member; and an elastic member coupled to the bobbin, wherein the cover member comprises an inner yoke extending from the upper plate of the cover member and disposed in the lateral plate of the cover member, wherein the bobbin comprises an accommodation groove formed on the outer peripheral surface of the bobbin, wherein the inner yoke is disposed in the accommodation groove, wherein the cover member comprises an escape groove formed on the inner yoke, wherein at least a portion of the escape groove is disposed higher than an upper end of the magnet, and wherein a width of a portion of the inner yoke gradually increases as an end portion of the inner yoke is approached.
 18. The voice coil motor of claim 17, wherein at least a portion of the inner yoke is disposed between one portion of the bobbin and another portion of the bobbin in a circumferential direction.
 19. The voice coil motor of claim 17, wherein the inner yoke comprises a connection portion bent from the upper plate of the cover member, and wherein the escape groove is disposed at a position adjacent to that of the connection portion of the inner yoke.
 20. A voice coil motor comprising: a cover member comprising an upper plate and a lateral plate extending from the upper plate; a bobbin disposed in the cover member; a coil disposed on an outer peripheral surface of the bobbin; a magnet facing the coil and disposed between the coil and the lateral plate of the cover member; and an upper elastic member coupled to an upper portion of the bobbin, wherein the cover member comprises an inner yoke extending from the upper plate of the cover member and disposed in the lateral plate of the cover member, wherein the bobbin comprises an accommodation groove formed on the outer peripheral surface of the bobbin, wherein the inner yoke is disposed in the accommodation groove, wherein the cover member comprises an escape groove formed on the inner yoke, and wherein the escape groove is overlapped with the upper elastic member in a direction perpendicular to an optical axis direction. 